---
id: fire-modes
title: Ultra and Rotary autocannon rates are a choice
status: open
dependsOn: [ev]
exitCriterion: >
  A Rotary AC is fired at a rate the bot chose against the jam risk, and a
  different rate is chosen when the risk is worth taking.
---

# fire-modes

Partly built. `Weapon::shots_per_firing` exists, `Mode`, `WeaponMode` and
`OneOf` are in `volley.rs`, and a launcher's modes already resolve through
`OneOf::resolve` - the type has no `sum` and no `iter` precisely so a caller
cannot add two alternatives together by accident.

What is not there is the *risk*. An Ultra AC firing double can jam; a Rotary
firing at four or six can jam harder. The bot picks a rate without pricing the
chance of losing the weapon for the rest of the match, which makes the highest
rate always look best.

## What it needs

- The jam roll per rate, from MegaMek rather than a rulebook. Probe it the way
  `SdsMinimumRange` probed range.
- A term in the volley's value for the expected cost of jamming: a weapon lost
  for the remaining rounds, weighted by how much of the force's firepower it is.
- A check that `ammo_spent` prices the higher rate correctly - it now counts
  rounds rather than declarations, so an Ultra in double mode should already
  spend two.